DESCRIPTION: Dr. Beemon proposes a series of studies to examine the regulation of processing of ALV/Rouse sarcoma virus (RSV) RNA. In Aim 1, a recently discovered CTE will be characterized. The main goal will be to identify and clone a cDNA encoding a cellular protein that binds to the CTE and is responsible for its activity. Xenopus oocyte injections will be used to test for function. In Aim 2, a negative regulator of splicing in the gag gene of RSV will be analyzed to determine what cellular splicing factors bind to it and what roles these might play in inhibiting splicing. In Aim 3 a set of studies will be performed to examine the role that deletion of a 42 bp sequence in the NRS plays in conferring pathogenicity on a variant of ALV that induces high incidence, rapid onset B cell lymphoma by insertional activation of c-Myb. Experiments will be performed to test whether deletion of this part of the NRS affects readthrough of viral transcripts and splicing to an acceptor in the c-Myb gene.